Incongruity sense of a driver due to dog clunking noise can be reduced with reduction of dog clunking noise. A fifth-speed driving gear (425) and a sixth-speed driving gear (426) are arranged on a driving shaft (41) along an axial direction. A first slider (451) is disposed to be movable in the axial direction between the fifth-speed driving gear (425) and the sixth-speed driving gear (426). The first slider (451) is not rotatable on the driving shaft (41). In the axial direction, the sum of the widths of the fifth-speed driving gear (425) and the sixth-speed driving gear (426) is smaller than the maximum width of the first slider (451).